Anchor-yield exposed column bases for minimizing residual deformations in seismic-resistant steel moment frames

This paper explores the concept of dissipative exposed column base connections by means of anchor rod yielding. This concept aims at enhancing the seismic performance of low-rise steel moment-resisting frames (MRFs). A mechanics-based model is proposed that explicitly simulates a broad range of damage mechanisms observed in exposed column bases. The model is implemented in a frame finite element analysis program, and its hysteretic performance is validated with experimental data available in literature. Incorporating this modeling feature in standard nonlinear response history analyses offers new insights in steel MRF responses. It is shown that when low-rise steel MRFs adopt a dissipative anchor-yield column base concept, they are less likely to experience residual story drift ratios during low probability of occurrence seismic events. It is also found that low-rise steel MRFs designed with nondissipative exposed column base connections are more prone to demolition than dissipative ones, due to their higher column residual axial shortening, particularly when ground motion duration is an important feature of the seismic hazard. Limitations of the present work are also discussed.